Researchers at the Mayo Clinic, Johns Hopkins Medicine and Wayne State University have demonstrated a novel sustained-release drug delivery system wherein dendrimers allow the delivery of steroids into the targeted cells, which have been causing damage through neuroinflammation, a major cause of retinitis pigmentosa and dry age-associated macular degeneration, thus paving the way to treat these incurable diseases.

As macular degeneration develops, clear, normal vision (shown left) becomes impaired by a general haziness. With advanced macular degeneration, a blind spot forms at the center of your visual field (shown right).

Retinitis pigmentosa and dry age-associated macular degeneration gradually damage the retina and can ultimately cause vision loss. The National Institute of Health estimated that over 7 million people in America are affected by macular degeneration and 1 in 4,000 Americans are affected by retinitis pigmentosa.

During the study carried out in part at the Kresge Eye Institute of the Wayne State University in partnership with the Ligon Research Center of Vision and College of Engineering of the Wayne State University, the nanoparticle delivery system was tested in rats that had neuroinflammation.

Iezzi stated that the drug delivery system targeted the inflammatory cells called microglial cells that are responsible for removing dying and dead material in the eye. The damage is caused by the cells through neuroinflammation when they were triggered as ‘trash collectors.’ The cells eat the dendrimers, which causes the release of the steroids into the cells, thus stopping their activity.

Kannan stated that the activated microglia cells selectively consume the nanoparticles, which have been retained in them for at least one month, thus making the sustained-release of the drug to provide the retina with a targeted neuroprotection. The approach decreased neuroinflammation development in the rats and protected their vision by eliminating damage to photoreceptors in the retina. While the steroids provide only short-term protection, the treatment collectively offers continuous protection against neuroinflammation.